Loudspeaker with improved voice coil support

ABSTRACT

A loudspeaker comprising a voice coil bobbin with a voice coil wound around its periphery is disposed in an annular gap formed between a columnar pole and a plate surrounding said pole. A plurality of terminals are mounted on the plate so that they are distributed on the circumference of a circle concentric with respect to the axis of said bobbin and mounted rotatably about their respective axes which are in parallel with the axis of said bobbin, with the terminals being coupled through suspension wires to the bobbin. The suspension wires may be of high resiliency, and have a layer of viscous resilient material surrounding the same. The voice coil bobbin of a loudspeaker may comprise a cylindrical body with a voice coil wound around its periphery, plural turns of a heat-resisting ribbon member impregnated with the thermosetting adhesives provided around the cylindrical body with the voice coil strip metal pieces inserted in between turns of the ribbon around the cylindrical body and aligned in the circumferential direction with a certain spacing left between respective ones so that both ends of each strip metal piece, project from the side edges of the ribbon, wherein projecting ends of the strip metal pieces are folded as to lie on the ribbon outer turn and these folded portions are heated to harden the thermosetting adhesives to fix the metal pieces to the ribbon.

United States Patent [191 Kinoshita [111 3,819,876 1 June 25,1974

Shouzo Kinoshita, Tokorozawa, Japan [75] Inventor:

[73] Assignee: Pioneer Electronic Corporation, Tokyo, Japan 221 Filed: Sept. 5, 1972 21 Appl. No.: 286,527

[30] Foreign Application Priority Data Sept. 4, 1971 Japan 46-80326 Sept. 4, 1971 Japan 46-80327 Sept. 4, 1971 Japan 46-80328 Sept. 4, 1971 Japan 46-80329 [52] US. Cl l79/1l5.5 VC, 179/115.5 R [51] Int. Cl H04! 9/04 [58] Field of Search 179/1 15.5 VC, 115.5 R; 181/31 R, 31 B [56] References Cited UNITED STATES PATENTS 1,907,687 5/1933 Van Lis 179/115.5 VC 1,960,016 5/1934 Knauf, Jr 179/1 15.5 VC 3,095,942 7/1963 Thibodeau 181/31 B 3,518,460 6/1970 Wood et al. 310/94 FOREIGN PATENTS OR APPLICATIONS 607,594 9/1945 Great Britain 179/] 15.5 R 776,280 6/1957 Great Britain 179/1 15.5 VC 889,967 2/1961 Great Britain 179/115.5 VC

Primary Examinerl(athleen H. Claffy Assistant Ekarninr Thomas L. Kundert Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A loudspeaker comprising a voice coil bobbin with a voice coil wound around its periphery is disposed in an annular gap formed between a columnar pole and a plate surrounding said pole. A plurality of terminals are mounted on the plate so that they are distributed on the circumference of a circle concentric with respect to the axis of said bobbin and mounted rotatably about their respective axes which are in parallel with the axis of said bobbin, with the terminals being coupled through suspension wires to the bobbin. The suspension wires may be of high resiliency, and have a layer of viscous resilient material surrounding the same. The voice coil bobbin of a loudspeaker may comprise a cylindrical body with a voice coil wound around its periphery, plural turns of a heat-resisting ribbon member impregnated with the thermosetting adhesives provided around the cylindrical body with the voice coil strip metal pieces inserted in between turns of the ribbon around the cylindrical body and aligned in the circumferential direction with a certain spacing left between respective ones so that both ends of each strip metal piece, project from the side edges of the ribbon, wherein projecting ends of the strip metal pieces are folded as to lie on the ribbon outer turn and thesefolded portions are heated to harden the thermosetting adhesives to fix the metal pieces to the ribbon.

7 Claims, 11 Drawing Figures FATBWED was an sum 2 OF 3 FIG] PATENTED JUH 2 5 I874 SHEET 3 0F 3 LOUDSPEAKER WITH IMPROVED VOICE COIL SUPPORT BACKGROUND OF THE INVENTION Field of the Invention This device relates to a loudspeaker of the type wherein a voice coil bobbin has a voice coil wound around its periphery and is disposed in an annular gap fonned between a columnar pole and a plate surrounding the pole.

SUMMARY OF THE INVENTION And, it is an object of the present invention to provide a loudspeaker device having an improved structure by which it provides superior sound characteristics relative to, such as, frequency and directivity, and which brings no deviation in sound reproduction characteristic between individual products.

And, it is an object of the present device to improve the support structure for supporting a voice'coil bobbin on a plate and to improve linearity while the bobbin is vibrating to thereby provide a loudspeaker having superior, particularly, frequency-, directivityand transient-characteristics.

It is an object of the present device to provide an improved voice coil bobbin so that it can be simply and reliably supported on a plate by means of dampers or suspension wires.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a fragmentary, perspective view of a main portion of a loudpseaker forming one embodiment of the present invention.

FIG. 2 is a partial, cross sectional view of a portion of the loudspeaker of FIG. 1.

FIG. 3 is a fragmentary, perspective view of the main portion of a loudspeaker forming a second embodiment of the present invention.

FIG. 4 is an elevational, cross sectional view of a portion of the loudspeaker of FIG. 3.

FIG. 5 is a fragmentary, perspective view of a main portion of a loudspeaker forming yet a third embodiment of the present invention.

FIG. 6 is a fragmentary, perspective view of a main portion of a loudspeaker forming a fourth embodiment of the present invention.

FIG. 7 is a side elevational view, a portion of which is partially enlarged, of a voice coil bobbin forming a portion of the embodiment of FIG. 5.

FIG. 7A is an enlarged sectional view of the connection for the bobbin of FIG. 7.

FIG. 8A is a perspective view of the voice coil bobbin of FIG. 6 during an initial stage of manufacture.

FIG. 8B is a perspective view of the voice coil bobbin of FIG. 8A after being partially wound.

FIG. 8C is a completed voice coil bobbin subsequent to manufacture by the process partially illustrated in FIGS. 8A and 88.

DESCRIPTION OF PREFERRED EMBODIMENTS In explaining one embodiment of the present invention in accordance with the drawings, particularly, in FIG. I, numeral 1 designates an annular magnet, wherein a discal yoke 2 is secured on one end face of the magnet I and an annular plate 3 is secured on the other end face of the same, a columnar pole 4 is secured on the yoke 2 so as to provide an annular gap of a predetermined width'between its peripheral surface and the inner periphery of the plate 3, and a magnetic circuit is formed by the aforementioned members.

About the upper end portion of the pole 4 is disposed a cylindrical voice coil bobbin 6 which has a voice coil 5 woumd around its periphery. The cylindrical assembly consisting of the bobbin 6 and the voice coil 5 wound therearound has an inner diameter slightly larger than the diameter of the pole 4 and an outer diameter slightly smaller than the inner periphery of the plate 3, and is disposed so as to be able to move freely axially within the gap formed between the pole 4 and the plate 3. It should be noted that numeral 7 designates a dome-shape diaphragm attached to one end of the bobbin 6.

Further, on the upper surface of the plate 3, a plurality of flanges 8 of a substantially cylindrical shape (in the illustrated device, the number is three) are secured. Respective flanges 8 are distributed and positioned on the circumference of a circle concentric with respect to the axis of the pole 4 with a certain spacing left between respective flanges. In a center hole 8a formed in the upper surface of the flange, as shown in FIG. 2, a threaded portion 9a of one end of a terminal 9 is inserted; and a nut 10 is screwed at that end. Between the terminal 9 and the upper surface of the flange 8 there are interposed a flat washer 11 and an insulating washer 12, while between the nut 10 and the lower surface of the flange 8 there are interposed a spring washer 13, a flat washer l4 and an insulating washer 15. If the nut 10 is screwed on the order of compression that the spring washer 13 is not compressed fully, the terminal 9 can rotate about its axis while being insulated electrically from the flange 8. It should be noted that a slit 9b having appropriate width and depth is formed at the top of the terminal 9.

A suspension wire 16 is inserted at one end in the slit 9b of the terminal 9 and secured thereto through a suitable process such as brazing. Wire 16 has a high resiliency and is made of material such as beryllium-copper alloy. This suspension wire 16 extends in a tangential direction, and terminates against the outer periphery of the bobbin 6 and is secured at one end to a terminal 17 attached on the bobbin 6.

To assemble the loudspeaker, the bobbin 6 is held in a certain position relative to the pole 4, the terminal 9 is rotated about its axis so that the opposite end of the suspension wire 16 attached to the terminal 9 will contact the corresponding terminal 17 of the bobbin 6, then the suspension wire 16 is brazed to terminal 17. When the above process is completed with respect to all suspension wires 16, the bobbin 6 may be held in the correct position where the axis of the bobbin lies on the axis of the pole 4 resulting in the intended sound characteristics. After the bobbin 6 is held on the terminals 17 through the suspension wires 16, each terminal 9 is bonded onto the flanges 8, respectively.

If one lead end of the voice coil 5 is connected to one of the terminals 17 attached to the bobbin 6 and the other end of the voice coil 5 is connected to one of the remaining terminals 17, there results that the voice coil 5 is electrically connected to two of the terminals 9 through the suspension wires 16, so that it is possible to connect the device externally by use of these terminals 9. However, if the lead ends of the voice coil 5 are connected externally through separate conductors,

there is no need of insulating the terminals 9 from the plate 3.

In explaining other embodiments of the present invention in accordance with the drawings, like numerals designate like elements to the device of FIGS. 1 and 2. In FIG. 3, the numeral 1 designates an annular magnet, wherein a discal yoke 2 is secured on one end face of the magnet l and an annular plate 3 is secured on the other end face of the same, a columnar pole 4 is secured on the yoke 2 so as to provide an annular gap of a predetermined width between its peripheral surface and the inner periphery of the plate 3, and a magnetic circuit is formed by the afore-mentioned members.

About the upper end portion of the pole 4, a cylindrical voice coil bobbin 6 is disposed which has a voice coil 5 wound around its periphery. The cylindrical assembly consisting of the bobbin 6 and the voice coil 5 wound therearound has an inner diameter slightly larger than the diameter of the pole 4 and an outer diameter slightly smaller than the inner periphery of the plate 3, and is disposed so as to be able to move freely in the axial directions within the gap formed between the pole 4 and the plate 3. It should be noted that numeral 7 designates a dome-shape diaphragm attached to one end of the bobbin 6.

Further, on the upper surface of the plate 3 a plurality of tying projections 29 (in the illustrated device, the number is three), are mounted by means of appropriate supporting members 28. Respective projections 29 are distributed on the circumference of a circle concentric with respect to the axis of the pole 4 and, as shown in FIG. 2, suspension wires 30 are secured at their respective stem portions to the tops of the projections through suitable fixing processes such as brazing. The suspension wire 30 extends in a tangential direction with respect to the outer periphery of the bobbin 6 and a contact portion is fixed to a terminal 31 attached on the bobbin 6. According to the above arrangement, the bobbin 6 can be supported resiliently in a certain position by the three suspension wires 30. Furthermore, each suspension wire 30 is provided at its stem end portion with a layer 32 of viscous resilient material so that it surrounds the end portion. This viscous resilient layer 32 may be made of suitable viscous resilient material such as silicone-rubber and absorbs vibration of the suspension wire 30 made of high resilient material such as beryllium-copper alloy to thereby prevent resonance of the latter.

In the loudspeaker constructed as above, because the voice call bobbin 6 is supported only by a plurality of suspension wires 30 extending in the tangential directions with respect to the bobbin 6, a preferably linearity is preserved in relation to an input signal to the voice coil 5 even in the case the bobbin 6 vibrates in its axial directions with a large amplitude. Further, even when the suspension wire 30 seems to provide the tendency that it resonates itself in response to vibration of the bobbin 6, the viscous resilient layer 32 surrounding the wire effectively absorbs vibration of the suspension wire 10, so that there results little deterioration of the frequency and transient characteristics which normally results from resonance of the suspension wire 30. The vibration absorbing effect of the viscous resilient layer 32 is more efi'ective if the shape of the viscous resilient layer 32 is selected so that it is thick at the stem end portion of the suspension wire 30 and becomes gradually thin as it approaches the pointed end portion of the same.

Furthermore, in case the suspension wire 30 is bent to give an appropriate curvature within a plane parallel to the axis of the bobbin 6, there results in the advantage that the compliance in the vibration directions of the bobbin 6 increases, the resistivity against flexing in directions normal to the vibration directions increases, and transversal rocking of the bobbin 6 is prevented.

Though in the above embodiment the dome-type loudspeaker is illustrated, it will be clear that the present invention can be applied to a cone-type loudspeaker.

ln explaining a third embodiment of the present invention, in FIG. 5, numeral 1 designates an annular magnet, wherein a discal yoke 2 is secured on one end face of the magnet l and an annular plate 3 is secured on the other end face of the same, a columnar pole 4 is secured on the yoke 2 so as to provide an annular gap of a predetermined width between its peripheral surface and the inner periphery of the plate 3, and a magnetic circuit is formed by the afore-mentioned members.

About the upper end portion of the pole 4, a cylindrical voice coil bobbin 6 is disposed which has a voice coil 5 wound around its periphery. The cylindrical assembly consisting of the bobbin 6 and the voice coil 5 wound therearound has an inner diameter slightly larger than the diameter of the pole 4 and an outer diameter slightly smaller than the inner periphery of the plate 3, and is disposed so as to be able to move freely in the axial directions within the gap formed between the pole 4 and the plate 3. It should be noted that numeral 7 designates a dome-shape diaphragm attached to one end of the bobbin 6.

On the upper surface of the plate 3 there are pro vided a plurality of fixing projections 29 (in the illustrated device, the number is three) with aid of appropriate supporting members 28. Respective projections 29 are positioned and distributed on the circumference of a circle concentric with respect to the axis of the pole 4, to the tops of these projections are stem portions of suspension wires 30' secured through suitable fixing processes such as brazing. The suspension wire 30' extends in a tangential direction with respect to the outer periphery of the bobbin 6 and is secured at its contact point with the periphery to a terminal 31 attached on the bobbin 6. According to the foregoing arrangement, the bobbin 6 is maintained in a proper position resiliently by three suspension wires 30.

In the loudspeaker device constructed as above, the voice coil bobbin 6 is supported only by plural suspension wires 30 extending in tangential directions relative to the bobbin periphery, so that the device preserves a sufficient linearity with respect to the input signal to the voice coil even when the bobbin 6 vibrates in its axial directions with a large amplitude.

Further, if the suspension wire 30 is bent to give an appropriate curvature in a plane parallel to the axis of the bobbin 6, the advantages will result that the compliance of the bobbin 6, in the direction of oscillation increases, the property of resisitvity against flexing of the same in directions normal to the vibration directions increases too, and transversal rocking of the bobbin 6 is prevented. Furthermore, if the projections 29 are kept in an electrically insulated state relative to the plate 3, and one end of the voice coil 5 and the other are connected, respectively, to one of the terminals 31 and another of the remaining terminals 31, it is possible to use the suspension wires 30 as take-out leads of the voice coil 5. In this case, wires 30' are not coated with viscous material as in FIG. 3.

Though in the above embodiments a device of the dome type is described, it will be understood that the present device can be applied to a cone type loudspeaker.

In explaining a fourth embodiment of the present invention in accordance with the drawings, particularly, in FIG. 6, numeral 1 designates an annular magnet, wherein a discal yoke 2 is secured on one end face of the magnet l and annular plate 3 is secured on the other end face of the same, a columnar pole 4 is secured on the yoke 2 so as to provide an annular gap of a predetermined width between its peripheral surface and the inner periphery of the plate 3, and a magnetic circuit is formed by the afore-mentioned members.

About the upper end portion of the pole 4, a cylindrical voice coil bobbin 6 is disposed which has a voice coil 5 wound around its periphery. The cylindrical 'assembly consisting of the bobbin 6 and the voice coil 5 wound therearound is disposed in a gap between the inner periphery of the plate 3 and the periphery of the pole 4 and resiliently supported by the plate 3 through a plurality of suspension wires 37 (in the illustrated device, the number is three) aligned in tangential directions so that the assembly can move in the axial directions.

In order to provide coupling means between the suspension wires 37 and the bobbin 6, a plurality of metal pieces 38 (in the illustrated device, the number is three) are attached to the bobbin 6 by means of a ribbon member 39, these pieces being distributed with a certain spacing left between respective ones and being aligned in the circumferential direction of the bobbin 6. FIGS. 7, 8A, 8B and 8C show an example ofthe steps of attaching the metal pieces 38 to the bobbin 6. According to the example, around the outer periphery of the bobbin 6 a heat-resisting ribbon member 39 is employed which is impregnated with thermosetting adhesives such as epoxy resin containing a setting agent, and one end of which is secured at an appropriate position on the outer periphery of the bobbin 6 through the process of hardening portions of the thermosetting adhesives by use of appropriate heating means such as a soldering iron 40 as shown in FIG. 8A. The ribbon member 9 fixed at one end to the bobbin 6 is wound around the bobbin 6 so as to form a first turn, and than a second turn is provided during which strip metal pieces 38 made of such as thin copper plate are disposed between the turns so that both ends of each piece project from the side edges of the ribbon member 39. After the ribbon member 39 is wound up, the other end of it is heated and bonded on the bobbin 6 (FIGS. 8B and 8C). The metal piece 38, after being folded at both end portions so that they wrap the ribbon member 39 positioned thereon, is secured to the ribbon member 39 by thermosetting adhesives processed by appropriate heating means (FIG. 7). As a result of the foregoing operation, the metal pieces 38 and the ribbon member 39 are rigidly secured, respectively, to the ribbon member 39 and the bobbin 6, and, even if the bobbin 38 is made of electrically conductive material, each metal piece 38 is electrically insulated from the other pieces and from the bobbin 36. Tops of the suspension wires 37 are secured to these metal pieces 38 through processes such as brazing.

Additionally, it is more effective to heat the bobbin after the afore-mentioned process in a heating oven in a range of a temperature permitting no damage to it for acting thermosetting adhesives.

Accordingly, the bobbin 6 and suspension wires 37 are very rigidly coupled one to another, as a result, the coupling portions will wear little even when the bobbon 6 vibrates heavily and suffers little secular variation.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a loudspeaker having a cylindrical voice coil bobbin with a voice coil wound about its periphery and disposed within an annular gap formed by a columnar magnetic pole and an annular plate surrounding said pole and spaced radially therefrom, the improvement comprising:

a plurality of terminals mounted on said plate in circumferentially spaced, concentric fashion, suspension wires made of a highly resilient material and extending volutely and tangentially to the bobbin and coupled respectively at their ends to said bobbin and to end portions of said terminals,

each of said suspension wires being curved within a plane parallel to the axis of the bobbin, and

a layer of viscous material surrounding a part of each wire and extending inward from said terminal.

2. The loudspeaker as claimed in claim 1, wherein said suspension wires are mounted on said terminals for rotation about respective terminal axes which are parallel with the axis of said coil bobbin.

3. The loudspeaker as claimed in claim 1, wherein said wires are formed of a beryllium-copper alloy.

4. The loudspeaker as claimed in claim 1, wherein said layer of viscous material comprises a siliconerubber.

5. The loudspeaker as claimed in claim 1, wherein said viscous material tapers from the terminal end towards the bobbin.

6. The loudspeaker as claimed in claim 1, further comprising: plural turns of heat resisting ribbon impregnated with a thermosetting adhesive wound about said voice coil bobbin, strip metal pieces inserted between the turns of said ribbon at circumferentially spaced positions, the ends of each of said strip metal pieces projecting beyond the side edges of the ribbon turn, the projecting ends of the strip metal pieces folded so as to lie on the ribbon outer turn, said folded portions being heated to harden the thermosetting adhesive and to thereby fix the metal pieces to said ribbon at said circumferentially spacd positions, and means coupling said suspension wires at their ends to respective m'etal pieces.

7. The loudspeaker as claimed in claim 1, wherein said terminals mounted for rotation about their individual axes, such that the end of the suspension wires attached to said terminal will extend readily toward said bobbin periphery, the opposite ends of said suspension wires are in turn brazed to bobbin terminals respectively, and said bobbin terminals are bonded to a ribbon wound about said voice coil bobbin. 

1. In a loudspeaker having a cylindrical voice coil bobbin with a voice coil wound about its periphery and disposed within an annular gap formed by a columnar magnetic Pole and an annular plate surrounding said pole and spaced radially therefrom, the improvement comprising: a plurality of terminals mounted on said plate in circumferentially spaced, concentric fashion, suspension wires made of a highly resilient material and extending volutely and tangentially to the bobbin and coupled respectively at their ends to said bobbin and to end portions of said terminals, each of said suspension wires being curved within a plane parallel to the axis of the bobbin, and a layer of viscous material surrounding a part of each wire and extending inward from said terminal.
 2. The loudspeaker as claimed in claim 1, wherein said suspension wires are mounted on said terminals for rotation about respective terminal axes which are parallel with the axis of said coil bobbin.
 3. The loudspeaker as claimed in claim 1, wherein said wires are formed of a beryllium-copper alloy.
 4. The loudspeaker as claimed in claim 1, wherein said layer of viscous material comprises a silicone-rubber.
 5. The loudspeaker as claimed in claim 1, wherein said viscous material tapers from the terminal end towards the bobbin.
 6. The loudspeaker as claimed in claim 1, further comprising: plural turns of heat resisting ribbon impregnated with a thermosetting adhesive wound about said voice coil bobbin, strip metal pieces inserted between the turns of said ribbon at circumferentially spaced positions, the ends of each of said strip metal pieces projecting beyond the side edges of the ribbon turn, the projecting ends of the strip metal pieces folded so as to lie on the ribbon outer turn, said folded portions being heated to harden the thermosetting adhesive and to thereby fix the metal pieces to said ribbon at said circumferentially spacd positions, and means coupling said suspension wires at their ends to respective metal pieces.
 7. The loudspeaker as claimed in claim 1, wherein said terminals mounted for rotation about their individual axes, such that the end of the suspension wires attached to said terminal will extend readily toward said bobbin periphery, the opposite ends of said suspension wires are in turn brazed to bobbin terminals respectively, and said bobbin terminals are bonded to a ribbon wound about said voice coil bobbin. 